SRC/clargv.f(3)

💅 NAME

SRC/clargv.f — bestie, this is a Fortran file from the Library Functions Manual and it's literally the home of clargv, ok?

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✨ SYNOPSIS

🎀 Functions/Subroutines

• subroutine clargv (n, x, incx, y, incy, c, incc) — CLARGV generates a vector of plane rotations with real cosines and complex sines.

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🫶 Function/Subroutine Documentation

🌸 the actual signature, no cap

subroutine clargv (integer n, complex, dimension( * ) x, integer incx,
    complex, dimension( * ) y, integer incy, real, dimension( * ) c, integer
    incc)

CLARGV generates a vector of plane rotations with real cosines and complex sines. That's the whole vibe 💫

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🦋 Purpose

okay so here's the deal, straight from the source:

!>
!> CLARGV generates a vector of complex plane rotations with real
!> cosines, determined by elements of the complex vectors x and y.
!> For i = 1,2,...,n
!>
!>    (        c(i)   s(i) ) ( x(i) ) = ( r(i) )
!>    ( -conjg(s(i))  c(i) ) ( y(i) ) = (   0  )
!>
!>    where c(i)**2 + ABS(s(i))**2 = 1
!>
!> The following conventions are used (these are the same as in CLARTG,
!> but differ from the BLAS1 routine CROTG):
!>    If y(i)=0, then c(i)=1 and s(i)=0.
!>    If x(i)=0, then c(i)=0 and s(i) is chosen so that r(i) is real.
!>

So like, it's cooking up rotations that zero out y(i) and stash the real good stuff in r(i). And note the conventions — same as CLARTG, but different from the BLAS1 routine CROTG. Don't mix them up bestie, iykyk 🙈

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💖 Parameters

• N

!>          N is INTEGER
!>          The number of plane rotations to be generated.
!>

literally just how many rotations we're generating ✨

• X

!>          X is COMPLEX array, dimension (1+(N-1)*INCX)
!>          On entry, the vector x.
!>          On exit, x(i) is overwritten by r(i), for i = 1,...,n.
!>

comes in as the vector x, leaves as r(i) for i = 1,...,n — she got a glow-up on the way out 💅

• INCX

!>          INCX is INTEGER
!>          The increment between elements of X. INCX > 0.
!>

the stride between elements of X. must be INCX > 0 — no zero, no negative, periodt

• Y

!>          Y is COMPLEX array, dimension (1+(N-1)*INCY)
!>          On entry, the vector y.
!>          On exit, the sines of the plane rotations.
!>

goes in as vector y, comes out holding the sines of the plane rotations 🌀

• INCY

!>          INCY is INTEGER
!>          The increment between elements of Y. INCY > 0.
!>

stride for Y, and again: INCY > 0 🫶

• C

!>          C is REAL array, dimension (1+(N-1)*INCC)
!>          The cosines of the plane rotations.
!>

the cosines, and they're REAL — main character energy, no imaginary part allowed 👑

• INCC

!>          INCC is INTEGER
!>          The increment between elements of C. INCC > 0.
!>

stride for C. INCC > 0, we been knew 💀

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👑 Author

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

the whole squad behind it, iconic honestly 🫡

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🌈 Further Details

!>
!>  6-6-96 - Modified with a new algorithm by W. Kahan and J. Demmel
!>
!>  This version has a few statements commented out for thread safety
!>  (machine parameters are computed on each entry). 10 feb 03, SJH.
!>

so 6-6-96 it got a whole new algorithm from W. Kahan and J. Demmel — slay. And this version has a few statements commented out for thread safety because machine parameters get computed on each entry. 10 feb 03, SJH. — noted, bestie 🧚

⚠️ heads up: those commented-out statements are a thread-safety thing, not a "clean this up" invitation. leave them alone 🙈

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⭐ Definition

Definition at line 121 of file clargv.f. that's the exact spot, fr fr ✨

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🍓 Author (of this page)

Generated automatically by Doxygen for LAPACK from the source code. a bot did this, and honestly? she ate 🤖💖

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and that's the whole page!! brought to you by LAPACK Version 3.12.0, for SRC/clargv.f(3) — mwah, go generate some rotations bestie 💜🎀